With the development of technology, more and more various portable electronic devices (such as smart phones or tablet computers) are equipped with a g-sensor for sensing the change of rotating angle of the portable electronic device itself. Specifically, if the change of rotating angle is greater than a predetermined value, the portable electronic device automatically rotates the displaying image 90 degrees, so that a user can watch or view the image more comfortable and convenient.
However, a user may have various motion states and usage modes while watching or viewing the images displayed by the portable electronic device, thus, the displaying image may have too high or too low rotation sensitivity if the rotation mechanism for rotating the displaying image is determined only based on the sensing result of the g-sensor. In other words, when the user sits down and uses the portable electronic device, the portable electronic device may not automatically rotate the image when the image is needed to be rotated. Or, when the user walks and uses the portable electronic device, the portable electronic device may automatically rotate the image when the image should not be rotated. Consequentially, it is quite inconvenient and uncomfortable for a user while using the portable electronic device to watch or view images.